This application relates to lasers, and more specifically, to optically-pumped lasers.
A laser generally includes an optical resonator, an active laser medium in the optical resonator, and a pump source. The active laser medium is selected to absorb the energy from the pump source and to produce an optical gain at a laser wavelength. The laser is optically pumped when the pump source is a laser or other light source. The resonator is used to direct the optical energy at the laser wavelength to repetitively pass through the active laser medium to be amplified and stored in one or more resonator modes. When the optical gain exceeds the total optical loss in the resonator, the laser oscillation occurs and the optical energy at the laser wavelength can be coupled out of the resonator as a laser output beam.
The present disclosure includes a laser that uses a whispering-gallery-mode microsphere as the laser resonator and the active laser medium. The microsphere is formed of a material that is doped to produce the desired optical gain for laser action at a laser wavelength. An angle-polished fiber coupler is implemented to couple an optical fiber to the microsphere so that a pump beam at a pump wavelength from a pump light source can be delivered through the optical fiber to the microsphere and coupled into a whispering gallery mode at the pump wavelength in the microsphere. In addition, the angle-polished fiber coupler is also used to couple the laser beam in a whispering gallery mode out of the microsphere and into the optical fiber.